I'm not an expert but I would look first at the radiators. If they have a
steam release valve, they are steam. If they are closed loop, that says hot
water regardless of shape. A single pipe definately says steam but two
pipes could be either.

Does the system also supply residential hot water for the tub and sink. If
so it probably is not steam but there may have been hybrid systems way back
when




"Dyvim" wrote in message
ups.com...
No sight glass. And forgot to mention that there's no circulatory pump
- it's a gravity system. I cross-posted with a photo at
http://forums.invision.net/Main.cfm?CFApp=2